Netflix’s latest true-crime documentary series, The Investigation of Lucy Letby, premiered in early 2026 and has quickly become one of the platform’s most watched and most discussed releases of the year. The four-part series meticulously examines the case of former neonatal nurse Lucy Letby, convicted in 2023 of murdering seven babies and attempting to murder six others at the Countess of Chester Hospital between June 2015 and June 2016 — a crime wave that shocked the United Kingdom and exposed deep failures in hospital oversight and whistleblower protection.

Directed by Bafta-winning filmmaker Sam Benstead and produced by ITN Productions for Netflix, the series does not attempt to retry Letby’s guilt — her convictions were upheld on appeal in 2024 — but instead focuses on how the murders went undetected for so long, how the hospital and senior doctors repeatedly failed to act on mounting concerns, and how the families of the victims were left to fight for answers when the system meant to protect their children instead protected itself.

The documentary opens with raw, never-before-seen 999 calls from frantic parents who rushed their suddenly deteriorating babies back to the unit, only to be told “these things happen” in premature infants. It then traces the slow-building suspicion among consultants Dr. Stephen Brearey and Dr. Ravi Jayaram, who noticed an alarming cluster of unexplained deaths and collapses whenever Letby was on shift. Despite raising alarms as early as 2015, their concerns were dismissed by hospital executives who feared reputational damage and preferred to attribute the deaths to natural causes or staffing shortages.

Interviews with the grieving parents are the emotional core of the series. Mothers and fathers describe the terror of watching their tiny, fragile babies suddenly stop breathing or collapse for no medical reason, the guilt they carried for trusting the hospital, and the crushing blow of learning years later that a nurse had deliberately harmed their children. One mother, whose son was among those killed, says: “We handed our baby over to people we thought were saving him. Instead, they were taking him from us.”

The series also features powerful testimony from whistleblower doctors who faced hostility and professional ostracism for speaking up. Dr. Brearey recounts being told to “stop making trouble” when he first raised concerns, while Dr. Jayaram describes the moment he walked into the unit and saw Letby standing over a baby whose breathing tube had been dislodged — a moment he reported but which was not acted upon for months.

Police bodycam footage, hospital CCTV stills, insulin test results, and shift pattern analysis are woven throughout, showing how Operation Hummingbird eventually built an overwhelming circumstantial case against Letby. The documentary includes excerpts from her police interviews, where she repeatedly denies wrongdoing and suggests the deaths were due to poor hospital conditions — claims the jury ultimately rejected.

Critics have praised the series for its restraint and respect for the victims. The Guardian called it “a necessary, unflinching piece of public-service television,” while The Times described it as “a devastating portrait of institutional failure and individual evil.” Viewer reactions have been intense, with many reporting they watched through tears and felt compelled to discuss NHS whistleblower protections and patient safety afterward. The series holds a 94% audience score on Rotten Tomatoes, with comments like “I had to pause after each parent interview — the grief is unbearable” and “This is one of the most important documentaries Netflix has ever released.”

The final episode includes a prison interview with Letby, where she continues to maintain her innocence and insists the deaths were the result of systemic failures rather than deliberate acts. The filmmakers present her words without editorial comment, allowing viewers to weigh them against the evidence that convicted her.

For anyone who followed the Letby case in real time — or is only now discovering its full horror — The Investigation of Lucy Letby is essential viewing. It is not sensationalist entertainment; it is a painful, necessary examination of how evil can hide in plain sight, how systems can fail the most vulnerable, and how truth can take years to surface.

All four episodes are now streaming on Netflix. Be prepared: this one will break your heart, challenge your trust in institutions, and stay with you long after the screen goes dark.